WASHINGTON, July 30 (Arshad Mohammed and Lesley Wroughton/Reuters) - Israeli and Palestinian negotiators on Tuesday gave themselves about nine months to try to reach an agreement on ending their conflict of more than six decades in U.S.-brokered peace talks.

The two sides held their first peace negotiations in nearly three years in Washington on Monday and Tuesday, a diplomatic victory for Secretary of State John Kerry, but one that foreign policy analysts believe has low chances of success.

Flanked by the chief negotiators for both sides, Kerry said he was well aware of the doubts but described the initial talks, which focused on process rather than substance, as constructive and positive.

Speaking after the meetings, which included a closed-door session with President Barack Obama at the White House as well as talks between the two sides without U.S. officials present, Kerry said peace was possible despite the obstacles.

While I understand the skepticism, I don't share it, Kerry said with Israeli Justice Minister Tzipi Livni and Palestinian chief negotiator Saeb Erekat at his side, adding all so-called final-status issues to end the conflict were on the table.

We cannot pass along to another generation the responsibility of ending a conflict that is in our power to resolve in our time, he added. They should not be expected to bear that burden, and we should not leave it to them.

The talks will go to a second round by the middle of August, Kerry said, adding that our objective will be to achieve a final status agreement over the course of the next nine months.

Kerry said Israel had agreed to take unspecified steps to ease the lives of Palestinians in the West Bank, which is ruled by a Palestinian Authority dominated by Abbas' Fateh faction, and the Gaza Strip, where the Islamist Hamas group holds sway.

Speaking to reporters later, a senior U.S. official declined to identify these but said they aimed to improve economic growth and added it's more than just removing roadblocks.

LITTLE DETAIL ABOUT TALKS

U.S. officials declined to describe this week's talks in any detail, saying secrecy was vital, and they said they did not yet know whether they would take part in the talks planned within two weeks in Israel or the Palestinian territories.

The United States is seeking to broker an agreement on a two-state solution, in which Israel would exist peacefully alongside a new Palestinian state created in the West Bank and the Gaza Strip, lands occupied by the Israelis since a 1967 war. The last direct talks collapsed in late 2010 over Israel's building of Jewish settlements in the West Bank.

The major final status issues to be resolved include borders, the future of Jewish settlements in the West Bank, the fate of Palestinian refugees and the status of Jerusalem.

Livni, the chief Israeli negotiator, sought to cast the talks in a positive light.

It's going to be hard, with ups and downs. But I can assure you that ... in these negotiations, it's not our intention to argue about the past, but to create solutions and make decisions for the future, she said.

Erekat said it was time to end the conflict. Palestinians have suffered enough, and no one benefits more from the success of this endeavor more than Palestinians, he said. It's time for the Palestinian people to have an independent, sovereign state of their own.

The resumption of negotiations is a rare moment of good news in the Middle East for the Obama administration, which has struggled to formulate a policy to try to end the civil war in Syria or to facilitate a democratic transition in Egypt.

Kerry, who has prodded and coaxed the two sides to resume negotiations in a flurry of visits to the Middle East during his less than six months in office, urged the Israelis and Palestinians to embrace reasonable, principled compromise.

ABBAS UNDERLINES TOUGH ISSUES

However, Palestinian President Mahmoud Abbas pointed to some of the tough issues still to be discussed, saying no Israeli settlers or border forces could remain in a future Palestinian state and that Palestinians deem illegal all Jewish settlement building within the land occupied in the 1967 Middle East war.

In a final resolution, we would not see the presence of a single Israeli - civilian or soldier - on our lands, Abbas said in a briefing to mostly Egyptian journalists.

Foreign policy experts voiced deep doubts about the chances of success for the peace talks, the latest in a long series of U.S.-brokered efforts that have so far failed, including former President Bill Clinton's 2000 Camp David push.

Among the many obstacles to any agreement are split opinions within both the Israeli and Palestinian publics.

Resuming talks is unpopular among some of Abbas' supporters in Fateh, let alone Hamas, which has condemned the effort. The politics are also difficult for Israeli Prime Minister Benjamin Netanyahu, with some of his coalition partners opposed to creating a Palestinian state.

The two warning signs for me are, first, you don't have the beginning of permissive politics in either Israel or Palestine, said Jon Alterman, head of the Middle East program at the Center for Strategic and International Studies think tank. This is not a diplomatic problem. It is fundamentally a political problem.

Second, a secretary of state is only as effective as the president he works for wants him to be and the president's body language has been to focus on the domestic economy and on disentangling the United States from wars in the Middle East, he added. (Editing by Alistair Bell, Christopher Wilson and Mohammad Zargham)